The present process relates to an improved process and apparatus for the preparation of uranium dioxide (UO.sub.2) by the calcining of a uranium compound, such as ammonium diuranate (ADU).
In the production of uranium dioxide, a particularly useful process involves the use of uranium hexafluoride and the preparation of an ammonium diuranate intermediate product, which ammonium diuranate is then calcined to produce uranium dioxide. As a general example of such processes, U.S. Pat. No. 3,998,925 teaches the preparation of ammonium diuranate from uranium hexafluoride by a continuous process. The ammonium diuranate serves as an intermediate product in preparation of uranium dioxide having good ceramic properties, with the ammonium diuranate calcined to uranium dioxide. Also, in U.S. Pat. No. 4,079,120, the calcination of ammonium diuranate to uranium dioxide is taught where a chute provided between the outlet of the calcining apparatus and a cooling conveyor is designed to be substantially completely filled at all times, and provide an airtight seal, so as to prevent influx of air into the chute where further oxidation might occur, and to prevent entry of air into the calcining apparatus.
In such processes, an off-gas stream is produced during the calcining of the ammonium diuranate, the off-gas stream containing finely divided uranium-containing particulate matter which must be removed from the off-gas stream. The off-gas stream also contains some ammonium fluoride which condenses as a tenacious solid material on surfaces that are at a temperature below the condensation temperature of the ammonium fluoride.
It is an object of the present invention to provide a process for the removal of uranium-containing particulate matter from the off-gas stream of an ammonium diuranate calcination process, without condensation of ammonium fluoride along with the separated particulate matter.
It is another object of the present invention to provide an apparatus usable in the separation of uranium-containing particulate matter, from the off-gas stream of an ammonium diuranate calciner, that prevents condensation of ammonium fluoride along with the particulate matter.